Other life in the Solar system?

[Kryten]

What he's trying to get across is that life requires a suitable solvent for the various reactions that comprise life to occur in. A huge number of the reactions in the life we know about would be impossible in a non-polar solvent, making it very hard to see how an organism could survive utilising such a solvent. That organisms may be able to use various non-polar substances in other ways is completely irrelevant.

[lajoswinkler]

We see life in both "too cold" and "too hot" conditions on Earth. Black Smokers melt submarine windows, but many lifeforms are pretty happy in there.

Oh no, we don't. We see "too cold" for humans and "too hot" for humans. There's nothing magical about hyperextremophiles. Their existence is noteworthy and fascinating, though.

Microbes don't live in the black smoker vents, they live around them. Temperatures of the fluid coming from the smoker are measured in hundreds of °C and no microbe can tolerate it because proteins not only break apart their intermolecular bonds, but also intramolecular ones.

The most extreme microbes live around the vents where the temperatures are around 80°C, which is their ecological optimum. They can live even at 120°C but don't prefer it.

Other animals that feed on them live at considerably greater distances from the vents where the temperatures are much lower.

Can't animals like tardigrades survive in vacuum?

No. They will reduce their size (water evaporation), crawl up and wait to die. It takes about a week or so before you can't revive them anymore. I was always cross with the media distorting scientific facts. Scientists say one thing, media ****s all over it and presents it to the public and thus modern myths are created.

I posted the link to show that life does live on non-polar molecules. Of course it doesn't live on liquid methane, because the tree of life on Earth is water based.

But we weren't talking about nutrition.

That's like saying; "Humans don't eat hamburgers, they oxidize carbohydrates."

No, it's not the same. Hamburgers are made of carbohydrates, and bicarbonate anion is not the same chemical as CO2. It's because of simplicity that we say plants eat CO2, but they really can't to anything with it before they dissolve and ionize it.

You can also sometimes hear about gaseous carbon in the terms of biogeochemical cycles of carbon, but that doesn't mean we've got 5000°C carbon vapor on Earth.

Or when radiological contamination is discussed about, there's cesium-137, but that doesn't mean there's actual metallic cesium anywhere.

It might seem as a semantic problem, but it's just a simplification that some people really should first note to others because not all people have enough knowledge about the subject matter to understand the difference.

But there is still movement, it's about 100 °C above absolute zero. It would be a very slow life form, but thats no reason for it not to work. Again, plants are a very slow life form.

These are exactly the reasons for it to not work.

There's still movement at absolute zero, too, but you won't see anything alive at that temperature.

Methane molecules are bumping around at Titan's surface, but the temperature is too low for any kind of organic chemical reactions. There's not enough activation energy. There can be organic reactions at ~100K but they would require very reactive chemicals, something impossible to find outside laboratories.

So to you a thinking block of iron is as likely as liquid methane base life form.

There are blocks of iron in space. Not pure (nothing is pure in nature), but we have them. Dense asteroids contain lots of iron.

http://en.wikipedia.org/wiki/File:Pallasite-Esquel-RoyalOntarioMuseum-Jan18-09.jpg

Isn't it more like; Polar molecules dissolve polar molecules and nonpolar molecule only nonpolar molecules?

There is such tendency, yes, but absolute statements such as this one are false and are used only in teaching. Water dissolves helium, too, and it's one of the most nonpolar "molecules" out there. The amount dissolved is measly, though.

What I'm wondering about is Chris McKay(and other astrobiologists) wrong about his hypothesis?

Of course hes not right because hes Chris McKay, but why would an astrobiologist propose such an idea?

I'm only talking about the surface. What happens deep inside? I don't know, but various processes are possible.

[Diche Bach]

i'm a strong believer in venus housing sulfer-based life in its upper atmosphere. scientists have discovered microbial life in clouds on earth(http://www.usnews.com/news/articles/2013/01/24/scientists-discover-microbial-life-in-storm-clouds), so it's a possibility.

Big difference between terrestrial bacteria in hailstones and life evolving in an atmosphere. As far a I know, all live evolved either in water or on land. I am not aware of any life that ever evolved in situ in Earth's atmosphere.

She and her team found that many of the bacteria present came from plant surfaces.

[nettcod]

Europa. 'Nuff said.

[Monkeh]

If we don't have some kind of drilling probe affair searching Europa in my life time then I shall die a most unhappy man.

Liquid water and stuff is all you need. That and time. CELLO!

[Idobox]

Lajoswinkler, you should be prudent when you claim something is impossible. People used to claim life could not exist without sunlight.

What pretty much agrees upon is that if life exists in liquid methane, it would be vastly different from the water based one we know. Life in a non-polar solvents could use many chemicals that are not stable in water, such as the highly reactive ones you were talking about. Obviously, proteins and RNA wouldn't work in methane, but saying that any form of life is impossible without them is a bit quick.

We have exactly one sample of life bearing environment, so making claims on what is needed for life to be possible is very risky.

That being said, nobody has been able to describe a convincing methane-based biology, and the possibility of such life is very dubious. If it existed, it would rely on very different chemicals principles than those used by Earth life.

Still, it appears much more likely than life in iron blocks.

Also, if you expose an animal to vacuum for two weeks, and after some time, it is able to move, feed and procreate, then by my definition, it survived. Of course it doesn't mean it could live there indefinitely, like I can survive underwater for one or two minutes, but couldn't live without air. And mainstream news tend to not focus on these details.

[lajoswinkler]

There were no obstacles to life without sunlight. It just wasn't discovered at that time in history.

There are obstacles to life in cryogenic liquids, plasma, solids and vacuum.

You seem to take a standpoint from someone who has very little experience in this field, therefore "anything goes". Well it doesn't.

Why do you think extremely reactive chemicals would even exist in nature? Nature doesn't allow it because of the laws of thermodynamics. Stuff tends to be in the lowest energy state. That's why you'll never ever find a planet with seas of liquid rubidium.

Proteins don't work? My question is - what other stuff could exist? Universe if filled with aminoacids and low peptides spontaneously form under certain conditions. Why should there be anything else and what could that be? When I look at the periodic table, I see no alternatives, and I'm not looking at it through eyes of a schoolboy. I'm taking into consideration years of college and experience. I see nothing.

There's a reason why life on Earth looks like this. It's because that's the simplest scenario. People often look at Earth as "not space" and "space is space therefore it must be radically different". Earth is a planet like every other planet out there.

Chemical reactions need activation energy to go forwad. There isn't enough of it in cryogenic liquids. You can bet on that because that's a fact. I'm actually not limiting myself to Earth life, but keeping an incredibly opened mind.

Surviving an event and living under conditions are two very different things. Nobody benefits from media lies except the media.

[Idobox]

The argument was something along the lines of "life needs energy, and all energy comes from the sun", the second statement was wrong.

You're saying life needs a polar solvent to allow proteins to work. I'm not sure life requires proteins.

I am not knowledgable in the field, I just hate it when people claim something is impossible, especially when talking about something like life or intelligence. We have only one example, we can't make assumptions on what is needed, we can only make assumptions on what is needed for a version close to what we know.

Oxygen and ozone are pretty reactive stuff, and we find some of it in many places. Sure, not oceans of it, but we still find some. And on Earth, life is building a crapload of very reactive stuff.

On the protein stuff, I don't understand your point. The universe is full of metal oxides, and they spontaneously form crystals. Why should there be anything else?

From the wiki page on hypothetical biologies (I didn't look very far), Asimov (who was also a biochemist, I didn't know) suggested something called poly-lipids. Apparently, water destroys some molecules through hydrolysis and interferes with the internal hydrogen bonding of complex molecules, something that wouldn't happen with methane.

About the temperature, even at very low temperatures, you will have some reactions. If your molecules have a thermal spectrum of energy, even at 1K, some will have enough energy. That will be extremely slow, but that will still happen, and I don't see why that forbids life.

If we take the rule of thumb of x2 per 10K for the speed of reaction, we get reaction happening 1 000 000 times slower in liquid methane. That's a few orders of magnitude slower than anything biologists are used to study, for sure, but it's still far faster than the geological timescale, so you will have to provide more information on why reaction can't happen. A cell dividing every 30 years might be long, but it's still observable.

All the media I have encountered talking about tardigrades or bacteria in space were talking of surviving, and explained it was as spores or other very specific forms of low metabolism. But that might be because I try not to consume the type of media that would deform that kind of news beyond recognition.

[K^2]

The temperatures we're talking about are cryogenic. The rates of reactions at such temperatures are close to zero.

Rates of reactions are governed not by temperature but by the relationship between temperature and activation energy, and guess what? Activation energies required to break down glucose are too high for these reactions to take place at any reasonable rate at room temperatures. Life on Earth is impossible, according to you. It's just too cold!

Fortunately, real world is significantly more complex, and activation energies can be lowered almost to nothing with suitable catalytic process. Without catalysts, life would not exist, but life is all about creating catalysts. Also known as enzymes, when they are protein-based.

And yes, as long as temperatures are high enough for you to have a solution to work with, they are high enough for catalyzed reactions to take place. Titan is plenty warm enough for some kind of life.

You've also made a point about water being needed as a polar solvent. That's also wrong. You can have a non-polar solvent with molecules in it that have polar and non-polar ends. Essentially, you add soap. Suddenly, your non-polar solvent acts as a polar one. Liquid methane will work just fine as a basis for life, so long as other organic molecules are present. And we do know that Titan's oceans are filled with all sorts of hydrocarbons.

So we do have an acceptable solvent. We do have a very significant energy and entropy flows. And we do have building blocks for complex life floating about. I wouldn't insist that this guarantees existence of life. Too much is uncertain about early evolution. But to say that life cannot exist in this environment is the highest level of naivety. This is precisely the kind of environment we are looking for.

Compared to that, every other place in the outer Solar system has fairly marginal odds of hosting life.

[lajoswinkler]

The argument was something along the lines of "life needs energy, and all energy comes from the sun", the second statement was wrong.

You're saying life needs a polar solvent to allow proteins to work. I'm not sure life requires proteins.

I am not knowledgable in the field, I just hate it when people claim something is impossible, especially when talking about something like life or intelligence. We have only one example, we can't make assumptions on what is needed, we can only make assumptions on what is needed for a version close to what we know.

Oxygen and ozone are pretty reactive stuff, and we find some of it in many places. Sure, not oceans of it, but we still find some. And on Earth, life is building a crapload of very reactive stuff.

On the protein stuff, I don't understand your point. The universe is full of metal oxides, and they spontaneously form crystals. Why should there be anything else?

From the wiki page on hypothetical biologies (I didn't look very far), Asimov (who was also a biochemist, I didn't know) suggested something called poly-lipids. Apparently, water destroys some molecules through hydrolysis and interferes with the internal hydrogen bonding of complex molecules, something that wouldn't happen with methane.

About the temperature, even at very low temperatures, you will have some reactions. If your molecules have a thermal spectrum of energy, even at 1K, some will have enough energy. That will be extremely slow, but that will still happen, and I don't see why that forbids life.

If we take the rule of thumb of x2 per 10K for the speed of reaction, we get reaction happening 1 000 000 times slower in liquid methane. That's a few orders of magnitude slower than anything biologists are used to study, for sure, but it's still far faster than the geological timescale, so you will have to provide more information on why reaction can't happen. A cell dividing every 30 years might be long, but it's still observable.

All the media I have encountered talking about tardigrades or bacteria in space were talking of surviving, and explained it was as spores or other very specific forms of low metabolism. But that might be because I try not to consume the type of media that would deform that kind of news beyond recognition.

The argument was flawed because even then people knew about Earth's inner heat.

Life certainly requires polymers for storing information, and complex organic molecules for building membranes. There is no life without membranes, they're essential. Again, thermodynamic talk.

So, by your criteria, anything is possible? That's a weird universe you're living in. Not everything can be.

Ozone is formed during lightning storms in poor amounts and is quickly destroyed. I won't include stratospheric ozone because that's not in the biosphere and exists because of UV irratiation of oxygen.

Oxygen is not extremely reactive. I'm talking about very reactive chemicals. Hypergolic stuff.

Neither do I understand you. Polylipids will be inert at cryogenic temperatures.

Again, you're making a fallacy similar to that Venus clouds stuff. For the life to evolve, active solvents and plenty of energy is required. If a hypothetical cell divides every 30 years in Titan's slush, it sure didn't evolve there, and neither would anything evolve inside clouds.

Evolving life requires special and stable conditions, and then after some time, products can take over the world.

I know what you mean by thermal spectrum of energy and I find it ridiculous. Indeed, inside a glass of liquid nitrogen there are hundreds of molecules with the temperature of Sun's surface. So what? Their amount is extremely low.

The rule of thumb doesn't work when the molecules responsible for organic reactions aren't working anymore. The rule breaks down.

I've read about the tardigrades on typical news portals.

Rates of reactions are governed not by temperature but by the relationship between temperature and activation energy, and guess what? Activation energies required to break down glucose are too high for these reactions to take place at any reasonable rate at room temperatures. Life on Earth is impossible, according to you. It's just too cold!

Fortunately, real world is significantly more complex, and activation energies can be lowered almost to nothing with suitable catalytic process. Without catalysts, life would not exist, but life is all about creating catalysts. Also known as enzymes, when they are protein-based.

And yes, as long as temperatures are high enough for you to have a solution to work with, they are high enough for catalyzed reactions to take place. Titan is plenty warm enough for some kind of life.

You've also made a point about water being needed as a polar solvent. That's also wrong. You can have a non-polar solvent with molecules in it that have polar and non-polar ends. Essentially, you add soap. Suddenly, your non-polar solvent acts as a polar one. Liquid methane will work just fine as a basis for life, so long as other organic molecules are present. And we do know that Titan's oceans are filled with all sorts of hydrocarbons.

So we do have an acceptable solvent. We do have a very significant energy and entropy flows. And we do have building blocks for complex life floating about. I wouldn't insist that this guarantees existence of life. Too much is uncertain about early evolution. But to say that life cannot exist in this environment is the highest level of naivety. This is precisely the kind of environment we are looking for.

Compared to that, every other place in the outer Solar system has fairly marginal odds of hosting life.

After all this talk, do you honestly think I've never heard of enzymes? There is not a concieveable enzyme architecture that would work at temperatures where molecules are barely moving.

Titan's surface is dead. I never said anything about its depths. For all I know and care, the depths might hold Kerbals.

The soap story is a nice one, but life won't work in cryogenic environments. Also, that world would have no chance of evolving in the first place.

Methane is a nonpolar molecule and its molecules behave like little inert balls, so it's close to ideal gas.

Liquid methane is held together by London forces and the fact its molar mass is not that low. It will not react with anything if we don't count in scary stuff made in research labs. Saying it can serve a valuable purpose for nursing life is completely ridiculous. It's the "anything goes" and "space is weird, Earth is not in space" talk.

[K^2]

After all this talk, do you honestly think I've never heard of enzymes? There is not a concieveable enzyme architecture that would work at temperatures where molecules are barely moving.

Barely moving? Titan's temperature is 1/3 of Earth's. Mean velocities will scale as a root of that, so they are more than half of these on Earth. In other words, increasing concentration 8-fold would result in comparable reaction rates. This is basic kinetics. Activation energy, similarly, would have to be about 3 times lower. Catalysts that lower activation energies by much higher fraction exist. Enzymes are among these.

So it is possible to get reaction going at reasonable rates both in case of concentration-limited and activation energy-limited reactions. No barriers left. What else are you going to come up with?

The soap story is a nice one, but life won't work in cryogenic environments. Also, that world would have no chance of evolving in the first place.

This isn't even an argument. You are just repeating your thesis without any kind of support for it. I have demonstrated that reaction rates can be reasonable. I have provided for an entirely reasonable workaround to polar solvent. We agree that all of the complex molecules required for both of these are present in the environment. We agree that there is ample source of energy for life. We have food, we have building blocks, and we have opportunity for metabolism. What else aren't you happy with?

As for "chance of evolving," all we know are conditions required for life to exist. And as far as anyone can tell, these are the conditions required for life to evolve. If special conditions exist, we don't know about them. Studying other worlds is the only way we will learn of such conditions if they exist. We do not know how life on Earth started, or even whether it started on Earth. And similarly, it is entirely possible that there is life on Titan that did not evolve on Titan originally.

Conditions on Titan do exist to support life. Processes consistent with metabolism are present. Of course, there are other explanations for such processes, but we have no direct indication of a dead world. The only way we will know for sure if there is life there is if we check for it. And whether we find it there or not, it will answer many questions.

[Idobox]

"Life certainly requires polymers for storing information, and complex organic molecules for building membranes. There is no life without membranes, they're essential. Again, thermodynamic talk."

No, life needs separation for evolution to happen. And guess what, there are other ways to create separation than phospholipid membranes.

One way is to use polar hydrocarbons to form membranes, an other is to use droplets of polar solvent in an emulsion.

"Oxygen is not extremely reactive."

Oxygen cause fires and explosions. Try to get a heat source close to a mix of carbon dust and oxygen to see. Or try to get any pure element in contact with oxygen and see what happens.

Anything that is a stronger oxydizer is scary as hell in my book.

"Evolving life requires special and stable conditions, and then after some time, products can take over the world."

This one is simply wrong. We simply don't know what is required for life to appear, we only have conflicting hypotheses about what might have happened on Earth.

If we use Schrödinger's definition of life, the only thing that is absolutely required is an energy gradient. There are probably other restrictions for life to happen, but with only one sample, we can't say anything about what is needed.

on the thermodynamic stuff, K^2 knows better than me, and I don't see the point in paraphrasing.

But on Titan, we have ethane being consumed as it goes close to the surface, probably reacting with hydrogen to form methane. That is the proof that significant chemistry can happen on organic molecules at that temperature. There is no known mineral catalyst that can account for that, so it is unknown chemistry happening there. I think everybody agrees abiotic processes are a simpler explanation, and are thus more likely to be the explanation to this imbalance, but if abiotic chemistry can happen, so can biotic.

Your whole argument is life needs these type of molecules, a polar solvent and a higher temperature. The temperature argument doesn't stand, the polar solvent is seriously questionned, and you can't prove that the molecules used by life on Earth are the only able to fulfill that function. In particular, there are a number of molecules that aren't stable in water, do you know enough in non aqueous low temperature organic chemistry to affirm no equivalent of amino acid chains can exist?

Finally, some people with more knowledge than me, that spend their whole day thinking of alternative chemistries for life, hired by prestigious entities such as NASA mananged to publish papers in peer reviewed journal explaining the basics of possible cryogenic methane based life. If refuting them was as simple as saying proteins don't work in cold methane, they probably wouldn't get published, or get hired in their current position.

[Moon Goddess]

I think the best chance if there is life in our solar system is some form of extremophile bacteria deep deep in europa at a thermal vent and we'll probably never be able to find them, or some form of radioautotrope, or some form or chemolithoautotrope deep in the bedrock of mars maybe a mile down or more. Even less likely we'll ever find those.

[lajoswinkler]

Barely moving? Titan's temperature is 1/3 of Earth's. Mean velocities will scale as a root of that, so they are more than half of these on Earth. In other words, increasing concentration 8-fold would result in comparable reaction rates. This is basic kinetics. Activation energy, similarly, would have to be about 3 times lower. Catalysts that lower activation energies by much higher fraction exist. Enzymes are among these.

So it is possible to get reaction going at reasonable rates both in case of concentration-limited and activation energy-limited reactions. No barriers left. What else are you going to come up with?

This isn't even an argument. You are just repeating your thesis without any kind of support for it. I have demonstrated that reaction rates can be reasonable. I have provided for an entirely reasonable workaround to polar solvent. We agree that all of the complex molecules required for both of these are present in the environment. We agree that there is ample source of energy for life. We have food, we have building blocks, and we have opportunity for metabolism. What else aren't you happy with?

As for "chance of evolving," all we know are conditions required for life to exist. And as far as anyone can tell, these are the conditions required for life to evolve. If special conditions exist, we don't know about them. Studying other worlds is the only way we will learn of such conditions if they exist. We do not know how life on Earth started, or even whether it started on Earth. And similarly, it is entirely possible that there is life on Titan that did not evolve on Titan originally.

Conditions on Titan do exist to support life. Processes consistent with metabolism are present. Of course, there are other explanations for such processes, but we have no direct indication of a dead world. The only way we will know for sure if there is life there is if we check for it. And whether we find it there or not, it will answer many questions.

Here's a typical enzyme.

(human alcohol dehydrogenase)

Let's not think about this particular enzyme. Let's consider their very srchitecture. Carbon chains with various attachements.

What do you think happens with complex organic systems at cryogenic temperatures, regardless of their environment? They crystallize because their very fabric crystallizes. I'm not talking about the macromolecule as a whole, with its special domains. I'm talking about its basic chains.

Give me an example of the basic huge molecular structure you think could stay normal at cryogenic temperatures. I dare you.

You haven't demonstrated the reaction rates are sufficient for any metabolism. You're holding onto a simplistic model that doesn't take into account that metabolic molecules work at all temperatures. Using your logic, we should be talking about very fast enzyme reaction rates at 2500°C, too.

No, life needs separation for evolution to happen. And guess what, there are other ways to create separation than phospholipid membranes.

One way is to use polar hydrocarbons to form membranes, an other is to use droplets of polar solvent in an emulsion.

I'm talking about membranes. Not phospholypid membranes per se.

There needs to be a separation, true, but a stable membrane is needed. A structure. Makeshift ones you're mentioning remind me of coacervates which might have played a role in early stages of abiogenesis and have never been proven to work at cryogenic temperatures.

Oxygen cause fires and explosions. Try to get a heat source close to a mix of carbon dust and oxygen to see. Or try to get any pure element in contact with oxygen and see what happens.

Anything that is a stronger oxydizer is scary as hell in my book.

We can talk about its bonds, and we can talk about the behaviour of pure element in bulk quantities. The latter is an artificial thing. Nature will not produce it.

There are far more reactive chemicals than oxygen, and you won't find them around in nature. They're inside special containers, or made in situ and exist as transient molecules in designed reactions.

This one is simply wrong. We simply don't know what is required for life to appear, we only have conflicting hypotheses about what might have happened on Earth.

If we use Schrödinger's definition of life, the only thing that is absolutely required is an energy gradient. There are probably other restrictions for life to happen, but with only one sample, we can't say anything about what is needed.

Life won't appear out of thin air. There is a huge gap between simple organic chemicals and first cells, and life is not a fixed point. You can't say "there, that's when life started".

We know one thing. It takes time. How could life evolve if the conditions are continuously changed? It can't. If there are no stable, special repetitive conditions over a long period of time, you can only expect increase in entropy and chemical balance, ie. loss of gradients.

on the thermodynamic stuff, K^2 knows better than me, and I don't see the point in paraphrasing.

But on Titan, we have ethane being consumed as it goes close to the surface, probably reacting with hydrogen to form methane. That is the proof that significant chemistry can happen on organic molecules at that temperature. There is no known mineral catalyst that can account for that, so it is unknown chemistry happening there. I think everybody agrees abiotic processes are a simpler explanation, and are thus more likely to be the explanation to this imbalance, but if abiotic chemistry can happen, so can biotic.

Are you referring to this article?

http://www.nasa.gov/topics/solarsystem/features/titan20100603.html

I don't share the hype. It reminds me of that "oxygen on Enceladus" news. If A can, so can B... That's being philosophical and not taking seriously the science behind it.

The reality is that NASA's astrobiologists need money, and the media likes sensational news. Remember the "arsenic life"? We already knew that As-substituded nucleic acids decompose spontaneously. Did that stop NASA from the hype? No. What else would astrobiologists do? They pump out models and hypotheses.

Titan's upper atmosphere is where the reactions happen. Sun irradiates stuff and it falls down, probably being fixed by the ground in exchange for something else. It might be a simple cryogenic geochemical circle... or observational mistake.

Other than that... the hot depths are where liquid water exists. Pockets of underground lakes with colder tops and hot vents, circulating water tainted with organic molecules for hundreds of millions of years in the same container - that's how you increase chances for abiogenesis.

Your whole argument is life needs these type of molecules, a polar solvent and a higher temperature. The temperature argument doesn't stand, the polar solvent is seriously questionned, and you can't prove that the molecules used by life on Earth are the only able to fulfill that function. In particular, there are a number of molecules that aren't stable in water, do you know enough in non aqueous low temperature organic chemistry to affirm no equivalent of amino acid chains can exist?

Finally, some people with more knowledge than me, that spend their whole day thinking of alternative chemistries for life, hired by prestigious entities such as NASA mananged to publish papers in peer reviewed journal explaining the basics of possible cryogenic methane based life. If refuting them was as simple as saying proteins don't work in cold methane, they probably wouldn't get published, or get hired in their current position.

We have no concieveable possible molecules other than organic polymers to begin with. If you know one, please inform me cause I have no idea. Everything made of carbon chains (and it will be carbon) is stiff at cryogenic temperatures.

Polar solvent is needed because it offers vastly more interactions. Solvent also needs to react (college org chem). Liquid methane is inert. Water and ammonia are reactive.

NASA's astrobiologist are primarily concerned by Titan's depths, and NASA's chemists about the atmosphere. I've yet have to read them talking about life on the frozen, inert surface.

I think the best chance if there is life in our solar system is some form of extremophile bacteria deep deep in europa at a thermal vent and we'll probably never be able to find them, or some form of radioautotrope, or some form or chemolithoautotrope deep in the bedrock of mars maybe a mile down or more. Even less likely we'll ever find those.

I think that, too.

[MBobrik]

As much as it can't make organisms live in vacuum, it can't make them live in stellar cores or liquid methane. There are limits.

.

small nitpick. While I agree on the stellar cores. I think creatures could adapt to living in vacuum or in an non-polar solvent given they've got suitable pre-adaptations and enough time to adapt. Of course starting in vacuum or in an nonpolar solvent is a completely other matter.

Edited September 16, 2013 by MBobrik

[lajoswinkler]

.

small nitpick. While I agree on the stellar cores. I think creatures could adapt to living in vacuum or in an non-polar solvent given they've got suitable pre-adaptations and enough time to adapt. Of course starting in vacuum or in an nonpolar solvent is a completely other matter.

Finally, someone understands the preadaptation in beneficial environments. Thank you.

Do you mean something like where life evolves under pressure and the organisms gradually venture towards the mountain tops that are in near vacuum, and they account for the constant inevitable evaporative loss by eating stuff?

Maybe. There needs to be a reason why would an organism go there. There's no reason for a species to go into the environment which is completely hostile except if it's sentient like humans. Other than some special stuff such organisms would crave that's concentrated on the mountain tops, I see no other possibilities, but even then it would be extremely difficult.

To add, if there is something in Europa or Mars or Enceladus, it will get to the vacuum surface only if it's expelled out from a geyser or muddy burp.

But to evolve life in vacuum and cryogenic conditions - no. Won't happen. The space is mostly vacuum and cryogenic conditions, and it's sterile. I'm baffled by the notion of constant fixation towards the insane ideas when we've got life on the third planet in the Solar system, and there's water and moderate temperatures. (-100 to +100°C, roughly). Evolving life is a tough one, so it will happen more often in conditions similar to the conditions we already know existed a long time ago here.

[Moon Goddess]

Finally, someone understands the preadaptation in beneficial environments. Thank you.

Do you mean something like where life evolves under pressure and the organisms gradually venture towards the mountain tops that are in near vacuum, and they account for the constant inevitable evaporative loss by eating stuff?

Maybe. There needs to be a reason why would an organism go there. There's no reason for a species to go into the environment which is completely hostile except if it's sentient like humans. Other than some special stuff such organisms would crave that's concentrated on the mountain tops, I see no other possibilities, but even then it would be extremely difficult.

You presume the lifeform goes there by choice.

Posit this scenario: Organism evolves on water rich planet with atmosphere. Organism adapts to high moutain thin atmosphere. Mountain organism adapts to higher ionizing radiation.

Planet geothermal ends slowly over a few million years, magnetic feild ends over a few million years. Organism adapts to further ionizing radiation.

Solar winds break down and strip atmosphere over the course of tens of millions of years, organism slowly adapts to less and less atmosphere and eventually to hard vacuum.

Still highly unlikely but possible at least.

[Idobox]

You haven't demonstrated the reaction rates are sufficient for any metabolism.

You're the one claiming reactions stop, that there is a lower limit on reaction rates under which it stops.

I'm saying it will slow down, possibly by a lot, but never really stops. Slow metabolism is still metabolism. If you put alcohol dehydrogenase in a flask of alcohol, keep it barely above the freezing point and wait a few years, what happens?

There needs to be a separation, true, but a stable membrane is needed. A structure. Makeshift ones you're mentioning remind me of coacervates which might have played a role in early stages of abiogenesis and have never been proven to work at cryogenic temperatures.

I've never said methanogenic life was definitely for sure possible, just that we don't know if it's impossible. If you dismiss anything that is considered reasonable but not proven to work as being utterly impossible, of course it is easy to assume life is impossible in liquid methane.

We can talk about its bonds, and we can talk about the behaviour of pure element in bulk quantities. The latter is an artificial thing. Nature will not produce it.

There are far more reactive chemicals than oxygen, and you won't find them around in nature. They're inside special containers, or made in situ and exist as transient molecules in designed reactions.

You won't find oxygen beyond trace levels anywhere but on Earth. Oxygen is very reactive, and will start hypergolic reactions with strong reducers. There is more reactive stuff than it, for sure, but you're tracing a line in the sand here.

Stronger oxidants than oxygen are found on other planets, like sulfuric acid or nitric acid, and the true nightmare stuff usually requires fluorine, a rather rare element, or chlorine, and I wouldn't be surprised to find traces of some in various atmospheres.

We know one thing. It takes time.

We don't know how much time. The oldest fossils are 3 billion years old, and some structures 3.5 Billion years old are disputed. It means life could have appeared very quickly once the rocks solidified.

We don't know if it takes weeks, years or millions of years for life to appear when the conditions are right.

In the case of Titan, the gradient comes from extra-planetary ionizing radiation, the gradient will be there for a long time..

Titan's upper atmosphere is where the reactions happen. Sun irradiates stuff and it falls down, probably being fixed by the ground in exchange for something else. It might be a simple cryogenic geochemical circle... or observational mistake.

The upper atmosphere is where H2 is produced. Part of it is blown away, part of it sinks, and the concentration drops to zero when reaching the ground, which means something is consuming it.

As noted, it could be a purely abiotic process, for example a catalytic reaction, except we don't know any mineral catalyst working efficiently at that temperature.

There is a mystery here, and if we assume the observations are correct, it will bring nice, shiny, new science.

We have no concieveable possible molecules other than organic polymers to begin with. If you know one, please inform me cause I have no idea. Everything made of carbon chains (and it will be carbon) is stiff at cryogenic temperatures.

Does it really need to be a pure carbon chain? couldn't something like a carbon chain with an Oxygen, Nitrogen or Sulfur in the middle do the trick? Remember that even if they're not stable in wet, oxygen rich environment at 300K doesn't mean they can't exist in cryogenic methane.

And some polymers are listed with glass transition temperatures as low as -125°C. Still hotter than liquid methane, but not that far away.

Are you referring to this article?

http://www.nasa.gov/topics/solarsyst...n20100603.html

When I talk of peer reviewed papers, I don't mean NASA pres releases.

The McKAy paper says that if there is methanogenic life on Titan, it will be widespread and have a large observable impact. He also shows there is plenty of energy for metabolism and that life breathing H2 would result in it being depleted at the surface, as well as liquid and solid complex organic molecules. It is a testable claim and a reasonable explanation of Cassiny-Huygens observations. He also cites low solubility in methane and low temperatures as issues, and addresses them.

1) http://www.sciencedirect.com/science/article/pii/S0019103505002009

2) http://www.scopus.com/record/display.url?eid=2-s2.0-0036766102&origin=inward&txGid=0FC44B2EA42EADE91AF4CE9BE14E1167.FZg2ODcJC9ArCe8WOZPvA%3a1

3) http://www.sciencedirect.com/science/article/pii/0273117787903589

4) http://www.springer.com/earth+sciences+and+geography/earth+system+sciences/book/978-3-540-20627-9

5) http://books.nap.edu/openbook.php?record_id=11919&page=74

Polar solvent is needed because it offers vastly more interactions. Solvent also needs to react

The last link briefly talks about the solubility problem, and paper 3 assumes large amount of dissolved stuff in methane.

What do you mean by solvents need to react? Water can be both a solvent and a reactive species, but I don't see why you would need a reactive solvent.

[MBobrik]

The last link briefly talks about the solubility problem, and paper 3 assumes large amount of dissolved stuff in methane.

The problem with methane ( and similar non-polar solvents ) is, that they suck at being solvents. they can dissolve only relatively small molecules. anything beyond certain ( as small as 6 carbons ) size will precipitate out. as opposed to polar solvents which can float even G dalton sized molecular behemoths.